This study was done to compare the protective effect of blood and crystalloid cardioplegia in patients with left ventricular dysfunction undergoing coronary artery bypass grafting (CABG). Sixty consecutive patients with left ventricular ejection fraction < 35% scheduled for CABG with the use of cardiopulmonary bypass without additional procedures were randomly divided into two groups. In the first group we used cold blood cardioplegia, in the second group cold crystalloid cardioplegia, both delivered only ortogradely. We measured hemodynamic data in early hours after operation, enzyme release and we collected other clinical data which could be influenced by perioperative myocardial protection. There was no death in either group. We also didn't find any significant difference in incidence of perioperative myocardial infarction, arrhythmias and use of intraaortic balloon pumping between both groups. In an early hours after operation in the group with blood cardioplegia we found significantly better hemodynamic data (LVSWI, RVSWI) and significantly lower enzyme release. We conclude, that cold blood cardioplegia shows superior perioperative myocardial protection resulting in earlier restoration of myocardial function. This difference could be important in patients with high degree of left ventricular dysfunction.